It is known that modern vehicle systems are conventionally equipped with a plurality of resistive sensors for monitoring the temperature value of several components of the vehicle system. At the present, the resistive temperature sensors, generally used, are negative temperature coefficient thermistor (NTC) or positive temperature coefficient thermistors (PTC).
The measure of the temperature values are made using a voltage divider consisting in a pull up resistance, having a known resistance value, connected in series to the resistive sensor at a common node. Two different voltage values are supplied respectively to a free end of the voltage divider to generate at the common node an analog signal indicative of the resistance of the resistive sensor.
The analog signal is then converted to a digital signal by means of an analog to digital (A/D) converter, which, in turn, is connected to a control unit, usually an engine control unit (ECU) provided in the vehicle system. The ECU uses the digital signal to determine the corresponding temperature of the resistive sensor based on the kind of sensor, NTC or PTC.
The NTC and PTC thermistors have characteristics that make complicated and costly the interfacing with the A/D converter. This is mainly due to the transfer function of the sensors that is non-linear. The non-linearity of the transfer function leads to a low accuracy of the measured resistance values and, as a consequence, of the temperature values.
In detail, the NTC thermistor has a very low resolution at low temperatures, i.e., temperatures close to approximately −30° C., at a point that it does not allow to verify if the thermistor is correctly operating. On the other hand, the PTC thermistor allows more precise measures at the low temperatures but it is more expensive than the NTC thermistor.
In view of the above, it is at least one object to improve the resolution accuracy of the determination of a resistance value of a resistive component. At least another object is to make the measure of the resistance value independent from electrical component tolerances. At least another object is to achieve the above-mentioned objects with a simple, rational, and rather inexpensive solution. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.